Non-woven articles are used in applications that require materials to be air permeable. Some applications of non-woven materials are surgical masks and filter membranes. Since many applications that use non-woven material are disposable, the non-woven materials should be easily manufacturable and low cost. Some methods of manufacturing non-woven materials are spunbonded and melt blown processes.
FIG. 1 illustrates the spunbonded process 10 for manufacturing non-woven materials. Thermoplastic fiber forming polymer 12 is placed in an extruder 14 and passed through a linear or circular spinneret 16. The extruded polymer streams 18 are rapidly cooled and attenuated by air and/or mechanical drafting rollers 20 to form desired diameter solidifying filaments 22. The solidifying filaments 22 are then laid down on a first conveyor belt 24 to form a web 26. The web 26 is then bonded by rollers 28 to form a spunbonded web 30. The spunbonded web 30 is then transferred by a second conveyer belt 32 and then to a windup 34. Spunbonding is an integrated one step process which begins with a polymer resin and ends with a finished fabric.
FIG. 2 illustrates the melt blown process 40 for manufacturing non-woven materials. Thermoplastic forming polymer 42 is placed in an extruder 44 and is then passed through a linear die 46 containing about twenty to forty small orifices 48 per inch of die 46 width. Convergent streams of hot air 50 rapidly attenuate the extruded polymer steams 52 to form solidifying filaments 54. The solidifying filaments 54 subsequently get blown by high velocity air 56 onto a take-up screen 58 thus forming a melt blown web 60. The web is then transferred to a windup 62. U.S. Pat. No. 4,380,570 entitled"Apparatus and Process for Melt-Blowing a Fiberforming Thermoplastic Polymer and Product Produced Thereby," describes the melt-blown process and is incorporated herein by reference in its entirety.
While non-woven materials can be manufactured by either the spunbonded or melt blown process there are difficulties associated with each process. For example, the newly manufactured non-woven material (e.g. melt blown web 60) tends to stick to the take-up screen 58. Further, the processes produce sheet material. Accordingly, to manufacture non-woven materials into three dimensional shapes, e.g. surgical masks and pleated filters, some form of post-processing is required.